Jump to content
Electronics-Lab.com Community


  • Posts

  • Joined

  • Last visited


bongo4000's Achievements


Newbie (1/14)



  1. what does the most recent schematic and part list for the 5A (or more) psu look like? i myself converted the 24V/3A psu to a 24V/6A version, which seemed to work well as long as i powered it from a lab psu for first test, but then it went up in smoke when connecting a 24V/200VA transformator. so i would like to see what you have changed when converting to higher current. thanx! bongo
  2. thanx! so where can i find the modified schematic and partlist for the redesigned psu? bongo
  3. hi audioguru i'm a bit puzzled. why do you call it a low voltage transformer? there are 2x 12v in series, so i think it's the same as the original project with the 24v. so why do i have to adjust these resistors? voltages are still the same! the changes against the original project, i'm aware of, are the additional 3055's to get 6A out of it, and the reduction of the series resistors for current sensing. i think i have not changed anything else. maybe i don't understand, but i think i have to do some changes to make it 6A proof. thanx! bongo
  4. so what modifications do you recommend to get the whole thing working reliable? (so i can go and look for new components) thanx! bongo
  5. so you think i have to use the ti OPA445AP to solve the problem?
  6. yea, this is exactly why the 1n5402 is there. i think when i add a diode as in your image, i have the problem that the input of U2 can have up to 30v, while this OP is not powered, and i don't think that the U2 is very happy with this situation ;-( why do you think that the 1n5402 is not enough? i think the blowing-up of the psu is more a problem of the current limitation which is not quick enough to limit the current on extreme overload. you don't think so?
  7. yes, the 25V have been there with the voltage control to 0V, and current control to 0A. so i connected a 1E resistor to the output, as i thought the voltage was because of a loaded cap. so i think, there was some over current for a short time, until the 1E resistor burnt away. i think this must have resulted in an over current through Q2, which burnt this one. no idea why the current limiter did not reduce this current. i think the base of Q4 is at vcc because it is pulled to vcc by Q2 ? rectifier seems to be ok, as voltages before the regulation (over the big caps) is ok. my idea to use a higher value for R15 was to limit the C-E current through Q2 to avoid that it burns down, when the output of the power supply is shorted. attached, you find my schematic for the 6A version. the trafo is 24V/200W thanx! bongo
  8. hi audioguru thanx for the quick response. i checked the neg supply, and it seems to be fine. btw: i always had 25v on the output, since i connected the trafo, although i had the voltage pots on 0v. (before, with the current limiting lab power supply instead of the trafo, it all worked well) so i removed the OP U1-3 to check the output stage by itself. the base of the 3055 is always at vcc, what looks really citical to me. so i pulled the signal, which is usually driven from U2 pin6, to low, which, i think, burnt up R15. i.e. the base of Q2 is always at vcc. is it possible that Q2 has been killed? how can this be avoided? would it be better to replace R15 by a resistor with higher impedance, to limit the current through Q2 for not killing it again? thanx! bongo
  9. for the first tests, i powered the circuit from a lab power supply with +25 v/ -5v. so it worked well. now that i connected the transformator and rectifier, the negative voltage dropped to about -1v. when i remove the OP U2, i again get the -5v. any idea what could be wrong?
  • Create New...